Myth: Seeing more bid requests means you can reach more users

Myth: Seeing more bid requests means you can reach more users

It sounds tautological — more requests in the bidstream means more opportunities, therefore more reach. Buyers chase exchanges that show the highest query volume.

The inflation in that number has a specific cause.

1. A single impression opportunity is frequently sent to many SSPs at once, and each SSP forwards it to your DSP. The same impression can hit your bidder five or six times under different path wrappers.

2. This is duplication, not reach. Counting raw bid requests counts the resale of inventory, not unique addressable impressions.

3. Worse, deduplication is non-trivial: the same impression arrives with different auction IDs, different SSP-side user IDs, and sometimes truncated request fields, so naive matching undercounts the duplication.

4. The metric that actually maps to reach is unique users (or unique impression opportunities) after collapsing duplicate paths — which you reconstruct from log-level data by fingerprinting requests (publisher + placement + user + timestamp window).

An exchange showing 2x the QPS of a rival may be offering less unique reach if its stream is more heavily resold.

Why it matters: bid-request volume measures how many times inventory is offered, not how many people you can touch. Reach lives in the deduplicated user count, and the raw stream hides it behind resale.